Hammer union and seal therefor

ABSTRACT

A hammer union comprises a thread end, a nut end and a hammer nut which, when cinched up, compresses a composite seal assembly thereby preventing leakage. The seal assembly comprises a metal insert of a size to pass into the seal groove of conventional hammer unions and a small seal acting between the insert, the thread end and the nut end. The small seal is conveniently an O-ring and is of a size that is compressed when the seal assembly is inserted into the thread end of the hammer union, thereby preventing the seal assembly from falling out of the threaded end when it is inverted.

This invention relates to an improved technique for sealing betweenmembers of a hammer union and more particularly to an improved sealassembly that replaces the existing seal of a hammer union.

BACKGROUND OF THE INVENTION

In the testing and production of hydrocarbon wells, specializedcouplings are provided which incorporate seals to prevent leakagebetween the coupling components. One such coupling is known as a unionand comprises a coarse male thread on one of the components whichcooperates with coarse female threads on a collar to provide a quickconnect/disconnect coupling.

A more specialized quick connect/disconnect coupling is known as ahammer union which comprises four components: a thread end having coarsemale threads on the exterior, a seal on the inside of the thread end, anut end having a smooth nose abutting the seal and a hammer nut havingcoarse female threads on the interior and ears on the exterior which maybe struck with a hammer to cinch up the coupling. Because hammer unionshave the capability of being quickly connected and disconnected, theyare widely used in temporary installations or in equipment which isexpected to be disassembled periodically.

Hammer unions have not been redesigned in many decades. The seal in aconventional hammer union is a large annular rubber seal that isbasically rectangular in cross section. One of the coupling componentsprovides a groove or rabbit receiving the annular rubber seal which iscompressed between the coupling components when they are cinched up,thereby providing a seal. The rubber component is exposed to gases,fluids and abrasives flowing in the interior flow passage of thecoupling. This conventional seal has withstood the test of time and hasbasically been unchanged for at least fifty years.

One of the situations where hammer unions are widely used is inequipment to test gas wells after they are initially completed or afterrecompletion from one zone to another. Typically, regulatory agenciesrequire that gas wells be tested to provide a measure of gasdeliverability and pressure using chokes of several different size. Toenforce these regulations, regulatory agencies often will not allow awell to be produced into a sales line before testing. Test equipmenttypically comprises a trailer having an inlet end for connection to thewell head, a separator for separating gas and liquid, an orifice meterfor measuring the gas from the well and an outlet for connection to aflow line leading to a flare.

Many gas wells, particularly those completed at depth, do not producecommercial quantities of natural gas until they are fraced. It is atribute to the research of major oil companies and major oil fieldservice companies that modern frac techniques convert large numbers ofconventionally completed uneconomic wells into economic ones. A typicalcurrent frac job injects a liquid or gel containing 500,000 or so poundsof sand or other proppant under pressure into a well to create,propagate and prop open a vertical fracture extending many hundreds offeet away from a well bore to provide a high permeability flow path froma relatively low permeability formation to the well bore.

One of the facts of life of fracturing a well with a large quantity ofsand or other proppant is that not all of the proppant stays in thehydrocarbon zone when the well is produced. When production starts, someof the proppant returns to the well bore and is produced at the surface.

Hammer unions are also widely used on drilling rigs to make mud lineconnections, to make connections in cementing operations and to pumpvarious liquids into a well bore during completion operations.

Disclosures of some interest relative to this invention are U.S. Pat.Nos. 2,726,104; 3,140,107; 3,848,905; 4,930,791 and U.S. PatentPublication H945.

SUMMARY OF THE INVENTION

In this invention, it is recognized that new gas wells, particularlythose that have been fraced, produce high velocity streams of proppantladen gas and liquid. Because the proppants are sand or similarparticles, they are quite abrasive. These high velocity abrasive wellstreams have the capability of cutting out the conventional seals usedin many flow line connections, specifically hammer unions. This createsa dangerous and awkward situation where highly flammable wellproduction, both liquid and gas, escapes from a flow line at a locationwhere it is unexpected. Instead of the well contents being flared at aflare installation hundreds of feet from the well head or test rig, allof a sudden, well contents are escaping in the test rig, immediatelyadjacent the well head or some other equally unsuitable location. Welltesters and others in the immediate area have to be vigilant to detectthe onset of large leaks in flow lines and test equipment and beprepared to shut the well in. It is a scary thing to shut in a wellproducing a high velocity stream loaded with proppant because of thedanger of cutting out valves on the well head, leaving the welluncontrollable.

In this invention, flow line coupling seals, such as in hammer unions,are modified to provide a seal largely protected against the abrasiveaction of high velocity well contents. Specifically, the conventionalall-rubber seal is removed and discarded. It is replaced by an annularmetal insert or carrier having a small annular groove or rabbitreceiving an O-ring or other much smaller seal. In this fashion, a sealprotected against the action of abrasive high velocity well fluids isplaced in the same groove as a conventional seal, meaning that the metalcomponents of a conventional flow line coupling, such as a hammer union,do not have to be machined or otherwise modified to accommodate a sealproviding a much longer useful life.

It is an object of this invention to provide an improved method andapparatus sealing a flow line coupling.

Another object of this invention is to provide an improved hammer union.

A further object of this invention is to provide a technique forchanging the seal of a flow line coupling without machining or otherwisemodifying the permanent metal components of the coupling.

These and other objects and advantages of this invention will becomemore apparent as this description proceeds, reference being made to theaccompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a conventional hammer union having aconventional seal assembly, certain parts being broken away for clarityof illustration;

FIG. 2 is a partial broken side view, similar to FIG. 1, of a hammerunion incorporating the seal assembly of this invention;

FIG. 3 is an enlarged partial side view showing a seal assembly of thisinvention in position in a thread end of a hammer union; and

FIG. 4 is an isometric view of the seal assembly of this inventionillustrating a metal insert and a resilient O-ring, certain parts beingbroken away for clarity of illustration.

DETAILED DESCRIPTION

Referring to FIG. 1, there is illustrated a conventional hammer union 10comprising as major components a thread end 12, a nut end 14 and ahammer nut 16.

The thread end 12 includes a short conduit 18 adapted to connect to aconduit or pipe, as by providing relatively fine exterior threads 20,such as machine threads or eight round threads. Very coarse exteriorthreads 22 are provided on the end opposite the threads 20. On theinside, the thread end 12 includes a flow passage 24 and an annulargroove or rabbit 26 communicating with the passage 24 for receiving alarge rubber seal 28. Typically, the groove or rabbit 26 includes anenlarged rim 30 for receiving a bulge 32 on the rubber seal 28 to assistkeeping the seal 28 in the groove 26. The seal 28 is an annular membermade of a rubber or rubber like material. The threaded end 12 terminatesin a more-or-less frustoconical seat 34 which may be straight orslightly concave.

The nut end 14 includes a short conduit 36 adapted to connect to a pipeor conduit having relatively fine exterior threads 38, such as machinethreads or eight round threads. On the inside, the nut end 14 includes aflow passage 40 communicating with the passage 24 providing a passagethrough the hammer union 10. The nut end 14 terminates in a nose 42having a more-or-less frustoconical face 44 mating with the seat 34 andproviding a seal seat 46 perpendicular to an axis of flow 48 through thehammer union 10.

The hammer nut 16 comprises a collar 50 of sufficient internal diameterto pass over the nut end 14 and the thread end 12 so the internalthreads 52 mate with the coarse external threads 22. The hammer nut 16includes a rim or shoulder 54 which engages a similar exterior shoulder56 on the nut end 14 thereby closing up the gap between the thread end12 and the nut end 14 upon threading the collar 50 onto the coarsethreads 22. The dimensions of the thread end 12 and the nut end 14 areselected such that cinching up the hammer nut 16 causes the seal seat 46to compress the seal 28 thereby preventing leakage between the threadend 12 and the nut end 14. The hammer nut 16 also includes a series ofears or projections 58 which may be manually grasped and turned orstruck with a hammer to cinch up the thread and nut ends 12, 14.Cooperation between the coarse threads 22, 52 provides a quickconnect/disconnect feature for the hammer union 10 and also allows easyconnection between the thread and nut ends 12, 14 even when the conduits18, 36 are not perfectly aligned. Those skilled in the art willrecognize the hammer union 10 to be a typical prior art hammer unionwhich has been manufactured and used in the drilling and production ofhydrocarbon wells for many decades.

The problem is that the seal 28 is exposed to liquids and gases passingthrough the flow path provided by the hammer union 10. When the hammernut 16 cinches up the thread end 12 and the nut end 14, there is atendency to compress the rubber seal 28 so it bulges out into the flowpassage 24. When using a hammer union 10 in a situation where the flowcontents are high velocity abrasive laden liquids or gases, there is atendency for the seal 28 to be eroded or cut out by the abrasives,particularly when it bulges out into the flow passage 24. When the highvelocity flow stream is a hydrocarbon liquid or gas, there is asignificant hazard because the leaking flow stream is highly flammableand is easily ignited.

Referring to FIGS. 2-4, this invention is illustrated. In FIG. 2, thestandard hammer union 10 has been modified by removing the conventionalseal 28, as with a screw driver, awl or other pointed instrument, andreplaced with a seal assembly 60 of this invention. The seal assembly 60comprises an annular metal insert or carrier 62 and a seal 64, typicallyan O-ring, much smaller than the seal 28. The seal assembly 60 isdesigned to provide a suitable resilient seal between the thread and nutends 12, 14 and protect the seal 64 from abrasion due to a high velocitywell stream flowing through the passages 24, 40, preferably withoutmodifying the metal components of the hammer union 10. This feature isimportant because it is much easier to simply replace the seal 28 withthe seal assembly 60 than it is to remove an existing hammer union fromservice, take it to a machine shop and have it machined in some manner,and then return it to service, bearing in mind that the hammer union maybe installed in a location many miles from the nearest machine shop.

To these ends, the insert 60 is made of any suitable metal such as onecomparable to the thread and nut ends 12, 14. The thickness of theinsert 60, i.e. the dimension parallel to the flow axis 48, isapproximately the same as, or slightly less than, the compressedconventional rubber seal 28. In this manner, the dimensional design ofthe conventional hammer union 10 is unaffected because the seat 34 andface 44 engage and stop movement of the thread and nut ends 12, 14. Theinternal diameter of the metal insert 62 is substantially the same asthe diameters of the flow paths 28, 40.

The external diameter of the metal insert 62 is more difficult toselect, mainly because there is some variation in the diameter of thegroove 26 from manufacturer to manufacturer and in unions of the samemanufacturer. It will be recollected that the prior art seal is a largerubber member capable of accommodating grooves of somewhat differentdiameter. Accordingly, the diameter of the groove 26 has not beentightly controlled in the past, mainly because there was no reason to.

If one were adapting a single hammer union, the external diameter of theinsert 62 has to be smaller than the measured diameter of the groove 26.If one were to adapt a large number of hammer unions of the same nominalsize, the external diameter of the insert 62 would have to be smallerthan all or a very large percentage of existing hammer unions. Thus, oneshould select an outside diameter of the insert 62 that is considerablysmaller than a large fraction of the grooves 26 of existing hammerunions. This means the seal 64 has to be relatively large and/orrelatively compressible to accommodate the gaps that occur between theinsert 60 and the groove 26.

The requirement that the insert 60 fit a large proportion of existinghammer unions introduces another problem. If the insert 60 is made smallenough in diameter to fit most existing hammer unions of the nominalsize under consideration, there is the tendency for the seal assembly 60will fall out of the thread end 12 if it is handled with the threads 20up. This is not fatal but it is very aggravating for the seal assembly20 to fall in the mud when the hammer union 10 is being assembled.Accordingly, the seal 64 is selected so its external diameter isnoticeably larger than the largest groove 26 so that when the insert 62and seal 64 are placed in the groove 26, the seal assembly 60 is wedgedin place by the seal 64. In other words, the seal 64 wedges the sealassembly 60 in place before the seal 64 is compressed by the seal seat46 of the nut end 16.

To these ends, the insert 62 comprises an annular metal member 66. Theinsert 62 might have separate grooves on its side and end but it is muchpreferred to provide a rabbit or groove 68 on an exterior edge facingthe seal seat 46 and the groove 26. The groove 68 accordingly includesan annular face 70 parallel to the flow axis 48 and a annular shoulderor face 72 perpendicular to the flow axis 48. The groove 68 accordinglyopens through the outside diameter of the insert 62 to face the threadend 12 and opens through the a rim or shoulder 74 to face the seal seat46. The groove 68 is typically a small fraction of the cross-sectionalsize of insert 60. A butt end 76 of the insert 62 abuts the groove 26and prevents movement of the insert 62 away from the seal seat 46 in acinched up position of the thread and seal ends 12, 14.

The seal 64 may be of any suitable cross-sectional shape, such assquare, polygonal or of compound shape but is preferably round, i.e. anO-ring. The seal 64 is preferably conventional rubber or rubberoidmaterial, which is used herein to mean that the seal has thecharacteristics of rubber, i.e. it is resilient, tolerant of hightemperatures and pressures and relatively chemically inert to compoundstypically found in hydrocarbon well streams. A preferred O-ring seal 64is made of Buna rubber and is available from any automotive supply storeor any industrial supply house.

After the old seal 28 has been removed, the metal insert 62 is droppedinto the groove 26 and the seal 64 is stretched over the shoulder 76 byinserting part of the O-ring 64 into the groove 68 and progressivelypushing or rolling the O-ring 64 around the shoulder 76 and into thegroove 68.

The single most common size hammer union is of a nominal 2″ internaldiameter has a nominal groove diameter of 2{fraction (11/16)}″. In fact,upwards of 80% of all existing hammer unions are of 2″ nominal diameter.Thus, making a seal assembly which may be used in all 2″ hammer unions,without having to machine any of the existing parts is a particularlyappealing feature of this invention. Thus, all of the dimensions belowrelate to 2″ hammer unions.

Hammer unions are made by a number of manufacturers, including FMCCorporation of Houston, Tex. The seal groove of a 2″ hammer union isstated to be 2{fraction (11/16)}″ but measuring a large number of 2″hammer unions showed something slightly different. The largest measuredgroove diameter was 2.687 inches and the smallest measured groovediameter was 2.660 inches. In order to make a seal assembly that fitsall existing hammer unions without machining existing parts, the metalinsert 62 of this invention is selected to be small enough to fit in thesmallest measured conventional hammer union and accordingly has amaximum size of 2.650 inches, including any tolerances, in diameter.Thus, the maximum size of the metal insert 62 is selected to be 2.650inches and a tolerance of plus zero, minus 0.005 inches.

The minimum diameter of the metal insert 62 depends on the size, designand compressibility of the seal 64. Because high pressure on the insideof the hammer union 10 produces an axial force and a radial forcetending to press the seal 64 into the corner between the hammer nut 16and the nose 42, it is easy to make the seal 64 perform satisfactorily.Thus, the metal insert 62 may have a loose tolerance on the small side.The minimum diameter of the metal insert is presently unknown because noattempt has been made to make an insert 62 of minimum diameter. However,a preferred minimum diameter is 2.535 inches which is the minimummeasured diameter of 2.660 inches less twenty five thousandths of aninch. Although it is believed that much smaller minimum diameters arefeasible because the O-ring seals may be made larger than stated below,a practical minimum size is on the order of 2.250 inches.

The thickness of the metal insert 62, i.e. the distance from the rim 74to the butt end 76 is also capable of substantial variation. Themeasured distance of a number of nominal 2″ diameter hammer unions, withthe groove 26 empty but with the hammer nut 16 made up, showed that thegroove 26 was more-or-less consistent at about 0.470 inches in lengthparallel to the flow axis 48. It is preferred that the nut end 14 andthe thread end 12 abut, or nearly abut, to provide a closed corner intowhich the seal 64 is compressed. Thus, the maximum thickness of themetal insert 62 is on the order of 0.470 inches and a preferred metalinsert is on the order of about 0.450 inches thick.

In a manner analogous to the selection of the minimum diameter of themetal insert 62, the minimum thickness of the metal insert 62 is subjectto wide variation because the seal 64 may be selected to be larger thanthe preferred dimension stated herein. No attempt has been made to makea satisfactory metal insert with a minimum thickness but a practicalminimum thickness is on the order of about 0.30 inches.

The groove 68 cut into the metal insert 62 is sized to receive asuitably sized seal, i.e. a seal that is large enough to seal againstthe thread end 12 and the nut end 14 in their made up condition.Although the groove 68 may be of any suitable size, in a preferreddesign for a nominal 2″ hammer union, the groove 68 is 0.165 inches on aside, i.e. the sides 70, 72 are 0.165 inches each. The seal 64 isselected to be of a size suitable for an insert 62 of the selecteddiameter and a groove 69 of the selected size. Although the seal 64 mayvary considerably, an O-ring having a nominal diameter of {fraction(3/16)}″, which in reality has a diameter of about 0.210 inches, hasproved suitable. Thus, an O-ring 64 suitable for this size insert is 2{fraction (11/16)} inches in outside diameter. A typical O-ring sealused in this invention is placed in the groove 68 by placing one sectionof the circumference of the O-ring over the rim 74 and rolling thebalance of the O-ring into the groove 68 with the thumbs.

The diameter of the groove face 70 is, analogous to the externaldiameter of the insert 62, subject to variation because the internaldiameter of the seal may vary substantially. For a nominal 2″ diameterhammer union with an O-ring seal 64 of {fraction (3/16)}″ nominalthickness and 2 {fraction (11/16)}″ nominal outside diameter, thediameter of the groove face 70 is conveniently about 2.313 inches with asmall tolerance.

Although this invention has been disclosed and described in itspreferred forms with a certain degree of particularity, it is understoodthat the present disclosure of the preferred forms is only by way ofexample and that numerous changes in the details of operation and in thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and scope of the invention as hereinafterclaimed.

We claim:
 1. A hammer union comprising a thread end having a conduitsection providing a first flow passage, a set of coarse externalthreads, a first groove for receiving a seal assembly and an outwardlydiverging mouth merging with the first groove, a nut end having a firstterminus providing a nose having a seal seat transverse to the firstflow passage and an outwardly diverging body merging with the seal seatand abutting the outwardly diverging mouth, a second terminus and asecond flow passage, between the first and second termini, communicatingwith the first flow passage, a seal assembly comprising an annular metalinsert received in the first groove and providing a second groove facingthe thread end and facing the seal seat, and a resilient seal in thesecond groove sealably abutting the thread end and abutting the sealseat and substantially isolated by the annular metal insert from thefirst flow passage, and a hammer nut comprising a collar surrounding thenut end and having coarse internal threads mating with the coarseexternal threads thereby captivating the thread end to the nut end,drawing the outwardly diverging body into abutting relation with theoutwardly diverging mouth and compressing the resilient seal and atleast one ear projecting from the exterior of the collar for receivingan impact from a hammer.
 2. The hammer union of claim 1 wherein thefirst groove is annular having a main seal receiving section ofgenerally rectangular cross section.
 3. The hammer union of claim 2wherein the first groove provides a rim of larger diameter than the mainseal receiving section.
 4. The hammer union of claim 1 wherein the metalinsert is loosely received in the first groove and capable of droppingout of the threaded end when the threaded end is inverted and the sealis of a sufficient size to wedge the insert in the first groove if thethreaded end is inverted.
 5. The hammer union of claim 4 wherein thehammer union is of a nominal 2″ diameter having a first groove of anominal 2{fraction (11/16)} diameter, the insert having an externaldiameter of not more than 2.650 inches.
 6. The hammer union of claim 5wherein the second groove is of square cross-section having a first faceparallel to the first flow passage and a second face perpendicular tothe first flow passage, the first and second faces having a dimension ofabout 0.165 inches.
 7. The hammer union of claim 1 wherein the seal isan O-ring.
 8. The hammer union of claim 1 wherein the seal is ofpolygonal cross-section.
 9. The hammer union of claim 1 wherein the sealis made of a material selected from the group consisting essentially ofrubber, rubberoid material and mixtures thereof.
 10. The hammer union ofclaim 1 wherein the second groove opens along an edge of the annularmetal insert.
 11. The hammer union of claim 1 wherein the metal insertprovides a butt end, a seal end, and an outer wall of cylindrical shapegenerally perpendicular to the butt end providing an external diameter,the second groove opening along an edge of the insert through the sealend and through a portion of the outer wall and having a face generallyparallel to the outer wall and spaced from the inner diameter, andwherein the resilient seal is an O-ring seal in the second grooveextending beyond the external diameter and beyond the seal end.
 12. Aseal assembly for a conventional hammer union of the type having athread end, a nut end, a hammer nut connecting the thread end and thenut end, the thread end and the nut end providing an axial flow passagetherethrough and a seal cavity therebetween having a length in thedirection of the flow passage, the length being variable between hammerunions, the seal cavity being bounded at one end by a non-adjustablerigid shoulder provided by the thread end and a seal seat on the nutend, comprising an annular metal insert providing a butt end forabutting the non-adjustable shoulder, a seal end for abutting the sealseat of the nut end, an internal diameter providing a flow passage andan outer wall of cylindrical shape generally perpendicular to the buttend providing an external diameter and having a groove opening along anedge of the insert through the seal end and through a portion of theouter wall and having a face generally parallel to the outer wall andspaced from the inner diameter, the insert being sized and shaped to fitinto the seal cavity and having an axial length parallel to the lengthof the seal cavity, the axial length of the insert being substantiallyless than the external diameter so the insert fits into the seal cavity;and a resilient seal in the groove extending beyond the externaldiameter and beyond the seal end, the metal insert substantiallyisolating the seal from abrasive contact with materials flowing in theflow path.
 13. The seal assembly of claim 12 wherein the seal is anO-ring, the O-ring being smaller, in an unstressed condition of theO-ring, than the groove internal diameter so the O-ring may be rolledinto the groove thereby tensioning the O-ring.
 14. The seal assembly ofclaim 12 wherein the seal assembly is for a nominal 2″ diameter hammerunion and the annular metal insert has an outer diameter of not greaterthan 2.650 inches and not less than 2.250 inches so the metal insertwill fit in an existing seal groove of nominal 2″ diameter hammer unionswithout machining the hammer union.